THE ISOLATION AND IDENTIFICATION OF THE PROSTHETIC GROUP RELEASED FROM A BOUND FORM OF ABSCISIC-ACID

A bound form of abscisic acid, herein called 'adduct', has been isolated from peas and barley and has been shown to release methyl abscisate upon mild acid, hydrolysis. Mass spectrometry of the methyl abscisate released by (H2SO4)-H-2 in (H2O)-H-2 showed that the remainder of adduct was linked as an enolate of the ketone of the moiety that releases methyl abscisate. Some evidence is adduced to suggest that adduct is a metabolic precursor of abscisic acid. The implications of the distribution of adduct between roots and shoots for the plant's response to stress is discussed.